This invention relates generally to recharging of batteries and more particularly to safety systems and methods suitable for battery recharging.
Electric vehicles are becoming more commonplace. However, nowhere are they encountered more frequently than on the golf course. For example, golf carts are heavily used by many different individuals and have to be recharged often. Existing battery chargers for these vehicles do not communicate with the vehicle being charged. Therefore, it is possible for a driver to attempt to operate a charging vehicle while that vehicle is still plugged into the charger, often producing disastrous results. Although this event is most often seen on the golf course today, it is a hazard that exists with all electric vehicles capable of being charged by being plugged in to an external power source, such as a wall outlet, or by plugging into any external charger.
At least one known prior art vehicle charging system uses an additional electrical wire connected between the charger and the vehicle other than the current carrying wires to detect when the vehicle is plugged into the charger. When the vehicle is connected to the charger, a warning light or other indication is displayed on the dashboard of the vehicle and/or the vehicle is prevented from running. Although effective, the addition of this extra wire adds to cost to the charging system and requires the manufacturing of special cords and receptacles.
One aspect of battery charging that makes it difficult to determine whether a battery in a vehicle is still connected to a charger is that, when fully charged, there is no current flowing in the connection and the battery voltage is equal to the charger voltage. One might place a relay or a solid state switch in circuit, so that charging current flows from the battery charger through the relay or switch and then to the battery. When the relay is opened or the switch is made non-conductive, a voltage would still remain on the charger side of the relay or switch if the charger were still connected, but no voltage would remain if the charger were not connected. Unfortunately, charging currents for vehicles are usually quite substantial, and the relay or switch would have to be able to carry the full amount of charging current while the battery is being charged. Thus, this approach to determining whether a vehicle is connected to a charger can be expensive and unpractical.